The use of optical technologies for numerous data communication applications is becoming more and more widespread. For example, the use of optical technologies in popular commercial sectors such as audio, video, personal communication devices and multimedia in general as well as the automotive industry is more and more widespread.
The increasing use of these technologies in popular consumer sectors gives rise to the need to reduce the production costs of the transmission/reception optical devices used in the communication systems based on said technologies. In particular, there is a strong tendency to reduce the production costs of the electro-optical modules which control the transmission/reception of the optical signals. The modules include optoelectronic components, such as optical transmitters or receivers, together with integrated electronic circuits or electronic components commonly required for the use of said optoelectronic components (amplifiers, filters, etc.).
One component which has a particularly high cost in the production of said modules is represented by the external covering (hereinafter also “package”), which generally acts as a protection against the external environment, as a mechanical support and as a shield against electromagnetic radiation for the optoelectronic and electronic components inside said module.
In the production of optical modules, packages made of plastic material are more and more commonly used as an alternative to traditional metal-type packages, notoriously much more expensive. However, the packages in plastic material used today have the drawback of not providing electromagnetic shielding for the module components and have the added disadvantage of being subject to infiltration by air and humidity from the outside, so provoking deterioration and reduced reliability of the optoelectronic and electronic components inside the module.
These problems are aggravated in those applications where the optical module is intended for use in unfavorable environmental conditions or where there is strong electromagnetic interference such as, for example, in the automobile sector. For example, optical networks made in accordance with the MOST Standard (Media Oriented System Transport), use low-cost optical modules and plastic fibers for connection between the various modules.
The use of the standard, initially developed for multimedia applications in the automobile sector, is gradually being extended to other sectors such as the consumers electronic sector (personal computers, home theater systems, etc.). At present, the optical modules used in systems conforming to the MOST standard include optical receivers and transmitters produced as two separate units, each unit comprising a molded plastic package provided with rheophores. Each package includes an optoelectronic component (for example a LED or a photodiode) and further includes electronic circuits associated, if necessary, to the optoelectronic component.
The optical transmitters and receivers so produced are mechanically fixed and electrically connected, by means of the rheophores, to electronic cards so as to form transceiver modules. These modules are provided with a further plastic package which also serves as an interconnection between the transceiver and the plastic optical fibers.
In the case of applications in the automobile sector, these transceiver modules are also normally incorporated into various forms of shielding for protection against electromagnetic emissions. All this complicates assembly and raises the final price of the transceiver module. Furthermore, a problem concerning the reliability of said transmission/receiving modules has been observed in that the optical transmitters and receivers which they contain, despite the fact that they are enclosed in respective molded plastic packages, are damaged by infiltration of humidity through the rheophores of the plastic package.